I had the same problem. But was eventually able to fix it.
For whatever reason it tries to read from files that don't exist. Or more specifically do exist but not in the place it thinks it should be.
Only way I was able to fix it was uninstalling EVERYTHING related to FSO and TSO. Then installing using the Official FSO Installer. When asked what path to use simply choose a name you will remember easily. Then install everything minus the Sleek launcher. After doing so then go back, choose same path if asked again and download the Sleek Launcher. When then launching the sleek launcher click "repair sleek launcher" and choose the same patch as before. Then hit update freeso and you should be good to go.
Also when asked I suggest having it at least add the icons to your desktop so you dont have to manually go and find the path and make your own short cuts.
Let me know if this worked or not. Cause I did some extra steps other then this to make everything work for me.